This application is based on Japanese Patent Application No. Hei 11-160852 filed on Jun. 08, 1999, No. Hei 11-305270 filed on Oct. 27, 1999 and No. 2000-129801 filed on Apr. 28, 2000 the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a hybrid type oil supplying apparatus and a method for controlling the apparatus having an internal combustion engine (engine) driven pump and an electric motor driven pump. For instance, the apparatus of the present invention can be applied to a system for supplying oil for lubrication or an oil pressure control.
2. Description of Related Art
An engine driven pump is driven by an output shaft of the engine. An engine driven pump supplies an amount of oil depending on a revolution speed. For example, the amount of oil is little at a low revolution speed such as an idle operation. In a lubrication purpose, if oil is not supplied sufficiently, lubricated portions might be sticked. On the other hand, in an oil pressure control purpose, if oil is not supplied sufficiently, a responsive ability is lowered. For example, in a case that an oil pressure is used for varying a width of a pulley of a continuously variable transmission, it is required to supply oil quickly into a chamber for actuating the pulley. Here, if oil is not supplied sufficiently, a time lag is generated at a changing operation.
On the other hand, at a high revolution speed, the amount of oil might be excessive, the engine load increases wastefully, and fuel efficiency might be lowered.
It is an object of the present invention to provide an oil supply apparatus to avoid an insufficiency of oil at low revolution speed.
It is another object of the present invention to provide an oil supply apparatus to avoid an insufficiency of oil at low revolution speed and to improve fuel efficiency.
It is a further object of the present invention to provide an oil supply apparatus requiring a small space to install it.
It is a still further object of the present invention to provide an oil supply apparatus in which a required amount of oil can be supplied from a starting of an engine.
It is a yet further object of the present invention to provide a controlling method of an oil supply apparatus in which a required transmission ratio can be provided from a starting of the engine.
According to a first aspect of the present invention, the present invention includes a pump driven by an engine and a pump driven by an electric motor. Therefore, the engine driven pump can be downsized so as to prevent an excessive oil supply. When an amount of oil supplied by the engine driven pump is insufficient, a required amount of oil can be supplied by, the motor driven pump. Further, it is possible to suppress the engine load and to improve fuel efficiency by downsizing the engine driven pump.
According to a second aspect of the present invention, the present invention includes an accumulator for accumulating oil discharged from the engine driven pump, and supplies oil in the accumulator through the motor driven pump. Since the motor driven pump is supplied oil accumulated at high pressure in the accumulator, the motor driven pump can introduce a sufficient amount of oil and the required amount of oil can be supplied through the motor driven pump even themotor driven pump has a low suction performance. Therefore, the motor driven pump can be downsized.
According to a third aspect of the present invention, in a case that a quick change of the transmission ratio is required, the accumulator supplies the accumulated oil through the motor driven pump.
According to a fourth aspect of the present invention, the motor driven pump is driven when a controller stops the engine. Therefore, the engine can be restarted when oil is supplied to the engine. For instance, it is possible to suppress a shock generated in the transmission because the engine can be restarted when the pressurized oil is supplied to an oil pressure control device of the automatic transmission. For instance, it is effective to drive the motor driven pump when the engine temporarily stopped by an operation of an idle-stop control. Further, in a belt type continuously variable transmission, the motor driven pump is controlled to maintain a pressure that can hold the belt. Here, a delay time from a stopping of the engine to a starting of the motor driven pump is preferably set according to a characteristic for maintaining the oil pressure. The motor driven pump may be controlled according to the oil pressure. For instance, the pump is stopped when the oil pressure increases more than a predetermined value, and the pump is driven when the oil pressure decrease less than a predetermined value. For instance, an applied voltage is decreased when the oil pressure increases, and the applied voltage increased when the oil pressure decreases.